Table 2-3 Cp15 Abbreviations; Figure 2-1 Cp15 Mrc And Mcr Bit Pattern - ARM ARM926EJ-S Technical Reference Manual

31
Cond
ARM DDI0198D
28 27 26 25 24 23 21 20 19
Opcode
1 1 1 0
_1
The mnemonics for these instructions are:
MCR{cond} p15,<Opcode_1>,<Rd>,<CRn>,<CRm>,<Opcode_2>
MRC{cond} p15,<Opcode_1>,<Rd>,<CRn>,<CRm>,<Opcode_2>
Attempting to read from a write-only register, or writing to a read-only register causes
Unpredictable results. In all instructions that access CP15:
• The Opcode_1 field Should Be Zero except when the values specified are used to
select the desired operations. Using other values results in Unpredictable
behavior.
• The Opcode_2 and CRm fields Should Be Zero except when the values specified
are used to select the desired behavior. Using other values results in Unpredictable
behavior.
Table 2-3 shows the terms and abbreviations used in this chapter.
Term
Unpredictable
Undefined
Should Be Zero
Copyright © 2001-2003 ARM Limited. All rights reserved.
16 15
L CRn Rd

Figure 2-1 CP15 MRC and MCR bit pattern

Abbreviation Description
UNP For reads: The data returned when reading from
this location is unpredictable. It can have any
value.
For writes: Writing to this location causes
unpredictable behavior, or an unpredictable
change in device configuration.
UND An instruction that accesses CP15 in the manner
indicated takes the Undefined instruction
exception.
SBZ When writing to this location, all bits of this field
Should Be Zero.
Programmer's Model
12 11 10 9 8 7 5 4 3
Opcode
1 1 1 1
_2

Table 2-3 CP15 abbreviations

0
1 CRm
2-5